Maternal age-specific rates of fetal chromosomal abnormalities in Korean pregnant women of advanced maternal age

OBJECTIVE: To evaluate the association of maternal age with occurrence of fetal chromosomal abnormalities in Korean pregnant women of advanced maternal age (AMA). METHODS: A retrospective review of the amniocentesis or chorionic villous sampling (CVS) database at Gangnam and Bundang CHA Medical Centers, between January 2001 and February 2012, was conducted. This study analyzed the incidence of fetal chromosomal abnormalities according to maternal age and the correlation between maternal age and fetal chromosomal abnormalities in Korean pregnant women ≥35 years of age. In addition, we compared the prevalence of fetal chromosomal abnormalities between women of AMA only and the others as the indication for amniocentesis or CVS. RESULTS: A total of 15,381 pregnant women were selected for this study. The incidence of aneuploidies increased exponentially with maternal age (P<0.0001). In particular, the risk of trisomy 21 (standard error [SE], 0.0378; odds ratio, 1.177; P<0.001) and trisomy 18 (SE, 0.0583; odds ratio, 1.182; P=0.0040) showed significant correlation with maternal age. Comparison between women of AMA only and the others as the indication for amniocentesis or CVS showed a significantly lower rate of fetal chromosomal abnormalities only in the AMA group, compared with the others (P<0.0001). CONCLUSION: This study demonstrates that AMA is no longer used as a threshold for determination of who is offered prenatal diagnosis, but is a common risk factor for fetal chromosomal abnormalities.